Uttaradit, 500 km (310 miles) north of Bangkok, was the worst hit province with 19 known dead and 92 missing, although officials there said the toll could be a lot higher.

"From what we've seen at the affected sites, we believe the toll will rise to a hundred as many might have still been buried under the mud," Uttaradit's deputy provincial health chief Eadyoungone Yongyuan told Reuters.

However, a senior Interior Ministry official said such speculation was yet to be confirmed.

"The estimate was based on the number of people reported missing and we are doing all we can to find those missing," Anucha Mokavetch told a Bangkok radio station.

Unusually heavy rain at the start of the monsoon, which lashed deforested hills and sent flash floods into villages and towns in five provinces, stopped in Uttaradit on Wednesday.

Water levels had receded, officials said, but showers were expected to continue until Friday.

Most of the deaths were believed to have occurred in the Laplae district of Uttaradit province, where heavy rain caused mudslides, officials said.

Prime Minister Thaksin Shinawatra flew to flood-stricken areas on Wednesday, a day after he formally took back the reins of power after a nearly two-month political break.

RESCUERS SLOG MILES

Rescue workers had to walk several kilometres (miles) into remote hill villages where one- and two-story houses were torn apart by the power of waters and covered in mud.

They were having difficulty getting heavy equipment into the area to search the wreckage, witnesses said.

A Buddhist temple in a village in Laplae was turned into a temporary shelter for 200 homeless villagers, they said.

Eight more people died in Sukhothai and Prae provinces, the Interior Ministry said.

In less severely hit towns, aid workers took to boats to take food to people stranded in their homes and take sick people to hospital.

"Drinking water is most needed now as tap water facilities have been damaged by the floods," Jarin Udomlert, a Laplae rescue official, told Channel 3 television.

Survivors have complained of a lack of early warnings of flash floods or mudslides from the government, but provincial officials said warnings had been issued, but ignored.

All rail traffic between Bangkok and northern province of Chiang Mai remained suspended on Wednesday, a day after four trains, carrying about 1,000 passengers, were stranded in Uttaradit, a state rail spokeswoman said.

The floods also forced prison officials to move 700 inmates from Uttaradit prison to jails in nearby provinces as their cells were about to be inundated, state Radio Thailand reported.